Accelerated reaction-driven carbon storage: Insights from laboratory-scale studies for field-scale geologic carbon storage

Accelerated reaction-driven carbon storage: Insights from laboratory-scale studies for field-scale geologic carbon storage Greeshma Gadikota Department of Civil and Environmental Engineering Environmental Chemistry & Technology Program Geological Engineering Program Wisconsin Energy Institute University of Wisconsin, Madison Contributions from Peter Kelemen, Columbia University & Greg Dipple, University of British Columbia National Academy of Science Workshop on Geologic Capture and Sequestration of Carbon Stanford University, Palo Alto, CA Gadikota and Park, 2014, in Carbon Dioxide Utilization: Closing the Carbon Cycle November 28, 2017

Carbon Mineralization at the Field Scale http://gwsgroup.princeton.edu/scherergroup/salt _Crystallization.html 2

CO 2 Storage in Geologic Reservoirs CO 2 Trapping Mechanisms Contribution to CO 2 Storage Security Solubility Trapping Mineral Trapping Mineral Trapping with Reactive Cracking Positive CO 2 stored as fluid Positive CO 2 stored as solid Facilitates CO 2 dispersion - reduces pressure build-up but increases CO 2 leakage potential Uncertainties in the time scales of carbon mineralization exist 3

Worldwide Availability of Ca- and Mg-bearing Minerals and Rocks Belvidere Mountain, Vermont Serpentine Tailings The most permanent method of carbon storage Mineral Carbonation of Peridotite Exothermic transformation Thermodynamically stable product Long-term environmentally benign and unmonitored storage Photo by Dr. Jürg Matter at LDEO (2008) 4

Direct versus Two-Step Conversion to Carbonates Gadikota and Park, 2014, Carbon Dioxide Utilization, 1st Edition, Elsevier 5

Reactivity of Ca- and Mg-bearing Minerals and Rocks and Implications for Carbon Storage Extent of Carbonation (%) 100 80 60 40 20 Experiments performed at 185 o C, P CO2 of 150 atm in 1.0M NaCl+0.64M NaHCO 3. 15 wt. % solid Reaction time: 0.5 hr 1 hr 4 hr 4 hr dry attrition grinding All others 1 hour dry attrition grinding O Connor et al., AAPG Annual Meeting, 2003 Fe 3 O 4 CaAl 2 Si 2 O 8 rock mixture Mg 3 Si 4 O 10 (OH) 2 Ca(Mg,Fe)Si 2 O 6 Mg 3 Si 2 O 5 (OH) 4 Fe 2 SiO 4 Mg 2 SiO 4 CaSiO 3 Ex-situ CO 2 Storage Shorter time scales (~hours) Limited spatial scale Relatively homogenous mineralogy More flexible tuning in reaction conditions Possible production of value-added products In-Situ CO 2 Storage Longer time scales (~years) Larger spatial scale with utilization of earth as a reactor (~hundreds of miles) Heterogeneous mineralogy Not limited by reactor size; Use of geothermal gradient Multiple CO 2 trapping mechanisms 0 Magnetite Anorthite Basalt Talc Augite Lizardite Antigorite Fayalite Forsterite Wollastonite No monitoring required Relatively economical at this time Alumino-silicates Abundance of less reactive minerals vs. limited availability of highly reactive minerals Silicates Carbonation efficiency defines whether mineral is utilized for ex-situ or in-situ storage 6

Role of Carbon Mineralization in Enabling Geologic Carbon Storage Develop thermodynamically downhill routes for permanent CO 2 storage with reduced monitoring needs To develop a comprehensive understanding of CO 2 mineralization behavior and its implications for CO 2 storage potential Comparison of dissolution rates and direct mineralization rates Determination of the feedback mechanisms due to chemo - morphological - mechanical changes Evaluation of the impacts on CO 2 storage potential and net CO 2 emission reductions & costs 7

Better Design of Kinetic Studies Gadikota et al., I&ECR, 2014 8

Laboratory Scale Dissolution Rates: Novel Reactor Designs to Probe Surface and Bulk Dissolution Custom-built Differential Bed Reactor to Determine Surface and Bulk Dissolution Rates Variations in surface dissolution vs. bulk dissolution rates observed in serpentine ((Mg,Fe) 3 Si 2 O 5 (OH) 4 ) Gadikota et al., I&ECR, 2014 9

Better Design of Kinetic Studies Gadikota et al., I&ECR, 2014 10

Minerals and Rocks of Interest I (single mineral) II (minerals and mixture rocks) Analyte Olivine (wt%) ((Mg,Fe) 2 SiO 4 ) Labradorite (wt%) ((Ca,Na)(Al, Si) 4 O 8 ) Anorthosite (wt%) Basalt (wt%) CaO 0.16 10.20 14.10 8.15 MgO 47.30 0.24 8.74 4.82 Fe 2 O 3 13.90 0.97 10.60 14.60 SiO 2 39.70 54.30 41.80 51.90 Al 2 O 3 0.20 28.00 24.20 13.40 Na 2 O 0.01 5.05 0.59 2.91 Carbonation Potential, (assuming that Fe does 0.343 0.171 0.105 0.076 not react to form FeCO 3 ) Carbonation Potential, (assuming that Fe 0.374 0.206 0.157 0.081 reacts to form FeCO 3 ) Mg# 1 87-66 48 An# 2-53 98 60 Anorthosite comprised 63% anorthite (CaAl 2 Si 2 O 8 ), 14% forsterite (Mg 2 SiO 4 ), 10% fayalite (Fe 2 SiO 4 ), and 3% albite (NaAlSi 3 O 8 ), and diopside (MgCaSi 2 O 6 ) Basalt comprised 20% anorthite, 25% albite, 8% diopside, 8% enstatite (MgSiO 3 ) 11

Chemo-Morphological Coupling during Carbon Mineralization: Effect of Reaction Temperature on Olivine Carbonation Extent of Carbonation (%) Cumulative Cumulative Internal Pore Void Volume Volume (ml/g) (ml/g) 100 80 60 40 20 0 10-2 10-3 10-4 TGA TCA ARC [1 hr] 80 100 120 140 160 180 200 Temperature ( o C) Unreacted Olivine 90 o C 125 o C 150 o C 185 o C 1 10 100 Pore Diameter (nm) Volume (%) 10 8 6 4 2 0 1 10 100 1000 Particle Diameter ( m) Experimental Conditions: P CO2 = 139 atm, 3 hrs, 1.0 M NaCl + 0.64 M NaHCO 3, 15 wt% solid, 800 rpm Temperatures > 150 o C are needed to achieve high conversions via direct carbonation Carbonate formation increases the particle size and reduces porosity Gadikota et al., 2014, Physical Chemistry Chemical Physics 12

Chemo-Morphological Coupling during Carbon Mineralization: Effect of Solution Composition on Olivine Carbonation Extent of Carbonation (%) 100 80 60 40 20 TGA TCA ASU [1 hr] 0 0.0 0.5 1.0 1.5 2.0 2.5 [NaHCO 3 ] (M) Concentration (mol/kg) 10-1 10-2 10-3 10-4 10-5 10-6 (b) Mg-equilibrium Carbonate - equilibrium 0.0 0.5 1.0 1.5 2.0 [NaHCO 3 ] (M) Speciation calculations show that NaHCO 3 buffers ph (6.4 7.0). Buffering the ph in the range of 6 7 facilitates dissolution and carbonation. Volume (%) 10 8 6 4 2 0 1 10 100 1000 Particle Diameter ( m) Unreacted D.I.Water 0.32 M 0.48 M 0.64 M 1.00 M 2.00 M Cumulative Cumulative Internal Pore Void Volume (ml/g) (ml/g) 10-2 10-3 10-4 Unreacted D.I.Water 0.32 M 0.48 M 0.64 M 1.00 M 2.00 M 1 10 100 Pore Diameter (nm) Progressive growth of carbonates reduces overall porosity and increases particle size. Experimental Conditions: 185 o C, P CO2 = 139 atm, 3 hours, 15 wt% solid, 800 rpm 13

Formation of Anhydrous MgCO 3 at Lower Temperatures Olivine Magnesite 185 o C II Relative Intensity 150 o C 125 o C 90 o C I Unreacted 20 30 40 50 60 70 80 2 Dominant formation of magnesite (MgCO 3 ) Hydrous phases such as nesquehonite (MgCO 3.3H 2 O) and hydromagnesite (Mg 5 (CO 3 ) 4 (OH) 2 4H 2 O) were not formed in the range of 90-185 o C 14

Direct Carbon Mineralization: Compositional Effects Reaction time 0.5 h 5.0 h 1.0 h 6.0 h * this study alumino-silicate bearing minerals or rocks silicate bearing minerals 15

Direct Carbon Mineralization: Effect of Passivation on Carbon Mineralization Rapid passivation in labradorite, anorthosite and basalt limit extent of carbonation but not for olivine! Experimental Conditions: 185 o C, P CO2 = 139 atm in 1.0 M NaCl + 0.64 M NaHCO 3, 15 wt% solid, 800 rpm Gadikota et al., in progress 16

Direct Carbon Mineralization: Effect of Reaction Time on Olivine Carbonation Olivine carbonation is wellmodeled as exhaustion of the Extent of Carbonation (%) remaining reactant at a constant rate. Experimental Conditions: 185 o C, P CO2 = 139 bars 1.0 M NaCl + 0.64 M NaHCO 3, 15 wt% solid, 800 rpm time (hours) 17

Comparison of Direct Mineralization Rates with Dissolution Rates: Olivine ((Mg, Fe) 2 SiO 4 ) vertical and horizontal ranges are constant on next several plots of temperature versus rate 0 to 250 C 10-13 to 10-2 mol/(m 2 s) Reaction Rate (mol/(m 2.s) Direct olivine carbon mineralization rates at higher CO 2 partial pressures are an order of magnitude greater compared to measured dissolution rates. Temperature ( o C) Experimental conditions for carbonation experiments : Minerals and rocks1-3 hours, 1.0 M NaCl + 0.64 M NaHCO 3 18

Direct Carbon Mineralization Rates: Comparison of Ca- and Mg-bearing Mineral and Rocks with Mine Tailings Reaction Rate (mol/(m 2.s) Olivine carbon mineralization rates at higher CO 2 partial pressures are two orders of magnitude greater than carbon mineralization rates for other common rocks and minerals. Temperature ( o C) Experimental conditions for carbonation experiments : Minerals and rocks 3 hours, 1.0 M NaCl + 0.64 M NaHCO 3 19

Comparison of Direct Mineralization Rates with Dissolution Rates: Brucite (Mg(OH) 2 ) and Serpentine ((Mg, Fe) 3 Si 2 O 5 (OH) 4 ) Reaction Rate (mol/(m 2.s) Temperature ( o C) Among peridotite alteration minerals, brucite dissolution is faster than olivine at low temperature, while serpentine minerals (chrysotile, lizardite) are much slower 20

Comparison of Dissolution Rates: Anorthite, Labradorite, Basalt, and Basaltic Glass vs Olivine Reaction Rate (mol/(m 2.s) With the exception of amorphous basaltic glass, olivine dissolution rates at temperature > 50 C are much faster than for basalt and alumino-silicate minerals such as plagioclase (anorthite, bytownite, labradorite, andesine) Temperature ( o C) 21

Comparison of Dissolution and Carbonation Rates at Low Temperature with Elevated CO 2 Reaction Rate (mol/(m 2.s) Brucite dissolves and carbonates faster than olivine High P CO2 increases dissolution and carbonation rates CO 2 Partial Pressure (bars) 22

Olivine Carbonation Kinetics over Similar Temperature Ranges Reaction Rate (mol/(m 2.s) 1/T (K -1 ) Experimental conditions for carbonation experiments : Minerals and rocks1-3 hours, 1.0 M NaCl + 0.64 M NaHCO 3 23

Olivine Dissolution Kinetics and Rate Laws log (r) E a = 52.9 kj/mol Mg (aq) :Si (aq) ph: 3.0 E a = 31 kj/mol 1/T (K -1 ) time (minutes) Our rate law: r 2042 2042 (0.1 ) ( 2.5 ) 2 T ( K ) 0.5 T ( K ) Mg, dis1( mol / cm. s) 10 ( H ) 0.003 10 6362.76 Hanchen s rate law: 2 0.46 T ( K ) Magnesite Precipitation Rate: (Saldi et al., 2012) r r Mg, dis2( mol / cm. s) 0.0854 ( H ) Mg, precip ( mol / cm 2. s) k Mg ( K OH a CO 2 3 K K CO CO 3 3 e K K OH OH K CO 3 a OH ) M (1 M Mg ) 24

Incorporating the Morphological Changes in the Kinetic Model 90 o C (Low) 125 o C (Medium) 150 o C (High) Temperature conditions chosen based on the single step carbonation rate data (Gadikota, PCCP 2014) Assume changing volume of rock due to surface passivation: n <0, increasing surfaces available (e.g., through fractures): n> 0 no changes: n = 0 Rate Rate time V V time time 0 time 0 n Simulations set up in PhreeqC (geochemistry software) 25

Carbonate Conversion Predictions Based on the Rate Data (a) (b) Our work T ( o C) r Mg,dis1, t = 0 (mol/m 2.s) 90 2.1 x 10-12 125 6.5 x 10-12 150 1.3 x 10-11 Hanchen et al., 2006 T ( o C) r Mg,dis2, t = 0 (mol/m 2.s) 90 1.4 x 10-11 125 6.7 x 10-11 150 1.7 x 10-10 Carbonation rates are highly sensitive to the temperature, rates of dissolution, and assumptions of changes in the morphology of the rocks Rates that are greater by an order of magnitude predict complete carbonation by a time difference of a decade => There is a critical need to constrain rates of mineral dissolution, carbonate precipitation, and coupled dissolution and precipitation behaviors 26

Role of Carbon Mineralization in Enabling Geologic Carbon Storage Develop thermodynamically downhill routes for permanent CO 2 storage with reduced monitoring needs To develop a comprehensive understanding of CO 2 mineralization behavior and its implications for CO 2 storage potential and costs Comparison of dissolution rates and direct mineralization rates Determination of the feedback mechanisms due to chemo - morphological - mechanical changes Evaluation of the impacts on CO 2 storage potential and net CO 2 emission reductions & costs 27

What is the Impact on Net CO 2 Emissions if Olivine is Reacted at 25 o C vs. 155 o C? 25 o C 155 o C Kirchofer et al., Energy & Envr. Sci., 2012 Experimental evidence of higher olivine carbonation kinetics at elevated temperatures translates into overall gains in reduced CO 2 emissions. 28

What is the Carbon Storage Potential via Ex-situ Mineralization Approaches? Kirchofer et al., Energy & Envr. Sci., 2012 Natural alkalinity sources a assumes a production rate of 18 Mt per year, equivalent to U.S. lime production, and b of 760 Mt per year, equivalent to U.S. sand and gravel production Carbon mineralization contributes to the portfolio of options available for reliable carbon storage. 29

Opportunities and Challenges in Accelerated Carbonate Formation for Industrial Decarbonization Gadikota et al., 2014, Journal of Hazardous Materials Gadikota et al., 2015, Advances in CO 2 Capture, Sequestration, and Conversion Variable compositions of industrial wastes can complicate the development of consistent processes May need high temperatures and pressures to achieve reasonable conversions Incorporate these materials into construction materials Safe for landfilling due to reduced alkalinity Control 20% SiO 2 10% csss Gadikota et al., 2015, Advances in CO 2 Capture, Sequestration, and Conversion 30

Opportunities in Accelerated Carbonate Formation for Industrial Decarbonization: Synthesis of High-Value Products Gadikota et al., 2015, Advances in CO 2 Capture, Sequestration, and Conversion Achieving high degree of control over desired chemical and morphological composition for CO 2 utilization remains a challenge Gadikota and Park, 2014, Carbon Dioxide Utilization, Elsevier 31

Preliminary Estimated Costs Storage approach US$/ton CO 2 Geologic carbon storage* 0.5-8 Geologic carbon storage: monitoring and storage* 0.1-0.3 Mineral carbonation* 50 100* Mine tailings carbonation with coproduction of value-added commodities (Ni) 10-60 *IPCC special report on carbon capture and storage, 2005 Grinding and milling ~ $10/ton of rock Chemical processing cost ~ varies from $ 10 - $ 50/ton of rock (path dependent) Cost estimates for mineral carbonation ~ $ 20 - $ 60 Offsets for costs include the production of value-added materials ~ $ 5 - $15/ton Feasible range for mineral carbonation: $ 5 - $ 45/ton 32

Conclusions and Summary Development of consistent experimental methodologies has led to an improved understanding of carbon mineralization rates. Significant variations in predicted mineralization rates translate into field scale uncertainties in monitoring costs. Mineralization rates are accelerated at higher temperatures and high pco 2 in situ carbon mineralization achieves high T and P at low cost ex situ potential for utilizing industrial waste heat may offset energy costs co-production of energy and useful commodities may offset overall costs Advanced mineralization approaches have the potential to be used in industrial decarbonization in addition to enabling clean fossil energy production. 33

Acknowledgments Peter Kelemen and Alissa Park, Columbia University Greg Dipple, University of British Columbia Funding Sources Geo-Chemo-Mechanical Studies for Permanent CO 2 Storage in Geologic Reservoirs NSF Research Coordination Network Carbon Capture, Utilization & Storage Accelerated CO 2 conversion to carbonates 34

Questions? 35

Chemo-Morphological Coupling during Carbon Mineralization: Effect of Reaction Temperature on Olivine Carbonation Extent of Carbonation (%) Cumulative Internal Void Volume (ml/g) 100 80 60 40 20 0 10-2 10-3 10-4 TGA TCA ARC [1 hr] 80 100 120 140 160 180 200 Temperature ( o C) Unreacted Olivine 90 o C 125 o C 150 o C 185 o C 1 10 100 Pore Diameter (nm) Volume (%) 10 8 6 4 2 0 1 10 100 1000 Particle Diameter ( m) Experimental Conditions: P CO2 = 139 atm, 3 hrs, 1.0 M NaCl + 0.64 M NaHCO 3, 15 wt% solid, 800 rpm Temperatures > 150 o C are needed to achieve high conversions via direct carbonation Carbonate formation increases the particle size and reduces porosity Gadikota et al., 2014, Physical Chemistry Chemical Physics 37

Chemo-Morphological Coupling during Carbon Mineralization: Effect of Solution Composition on Olivine Carbonation Extent of Carbonation (%) Volume (%) 100 80 60 40 20 TGA TCA ASU [1 hr] 0 0.0 0.5 1.0 1.5 2.0 2.5 [NaHCO 3 ] (M) 10 8 6 4 2 0 1 10 100 1000 Particle Diameter ( m) Unreacted D.I.Water 0.32 M 0.48 M 0.64 M 1.00 M 2.00 M Concentration (mol/kg) Cumulative Internal Void Volume (ml/g) 10-1 10-2 10-3 10-4 10-5 10-6 10-2 10-3 10-4 (b) 0.0 0.5 1.0 1.5 2.0 [NaHCO 3 ] (M) Unreacted D.I.Water 0.32 M 0.48 M 0.64 M 1.00 M 2.00 M 1 10 100 Pore Diameter (nm) Mg-equilibrium Carbonate - equilibrium Speciation calculations show that NaHCO 3 buffers ph (6.4 7.0) Buffering the ph in the range of 6 7 facilitates dissolution and carbonation Progressive growth of carbonates reduces overall porosity and increases particle size Experimental Conditions: 185 o C, P CO2 = 139 atm, 3 hours, 15 wt% solid, 800 rpm 38

Formation of anhydrous MgCO 3 at lower temperatures Olivine Magnesite 185 o C II Relative Intensity 150 o C 125 o C 90 o C I Unreacted 20 30 40 50 60 70 80 2 Dominant formation of magnesite (MgCO 3 ) Hydrous phases such as nesquehonite (MgCO 3.3H 2 O) and hydromagnesite (Mg 5 (CO 3 ) 4 (OH) 2 4H 2 O) were not formed in the range of 90-185 o C 39

Direct Carbon Mineralization Rates: Comparison of Ca- and Mg-bearing Mineral and Rocks with Mine Tailings Brucite mine tailings (vol % CO 2 at 1 atm) 100% 50% 10% 0.04% Experimental conditions : Minerals and rocks: 185 o C, P CO2 = 139 atm, 3 hours, 1.0 M NaCl + 0.64 M NaHCO 3 Brucite (Mg(OH) 2 ) mine tailings: ambient temperature, reaction time > 70 hours (Harrison et al., ES&T, 2013) *Rate data normalized to BET surface area 40

Comparison of Direct Mineralization Rates with Dissolution Rates: Olivine ((Mg, Fe) 2 SiO 4 ) Reaction Rate (mol/(m 2.s) Direct olivine carbon mineralization rates at higher CO 2 partial pressures are an order of magnitude greater compared to measured dissolution rates. Temperature ( o C) *Rate data normalized to geometric surface area 41

Comparison of Direct Mineralization Rates with Dissolution Rates: Brucite (Mg(OH) 2 ) and Serpentine ((Mg, Fe) 3 Si 2 O 5 (OH) 4 ) direct mineralization rates of brucite bearing mine tailings Reaction Rate (mol/(m 2.s) ( 4 vol%) (100 vol% CO 2 ) ( 50 vol% CO 2 ) ( 10 vol% CO 2 ) Temperature ( o C) *Rate data normalized to geometric surface area At low CO 2 concentrations (~4 vol. %), direct mineralization rates of brucite mine tailings are comparable with dissolution rates. Reaction rates increases with CO 2 concentrations. 42

Comparison of Direct Mineralization Rates with Dissolution Rates: Anorthite, Labradorite, and Basalt Shaded region represents direct mineralization rates of labradorite, anorthite, and basalt Reaction Rate (mol/(m 2.s) Direct mineralization rates are 1-2 orders of magnitude higher compared to dissolution rates of anorthite, labradorite, and basalt Hypothesis: Continuous removal of carbonate ions in solution to form solid precipitates drives the forward dissolution reaction rate => higher direct mineralization rates Temperature ( o C) *Rate data normalized to geometric surface area 43

Magnesite Formation in Fractured Porous Media: Evidence of Chemo-Morphological-Mechanical Coupling During Carbon Mineralization (a) (b) Evidence of magnesite formation along olivine fractures 44

Rate Data for Predicting the Time Scale of Carbonate Formation E a = 52.9 kj/mol E a = 31 kj/mol Our rate law: Hanchen s rate law: Magnesite Precipitation Rate: (Saldi et al., 2012) r r r 2042 2042 (0.1 ) ( 2.5 ) 2 T ( K ) 0.5 T ( K ) Mg, dis1( mol / cm. s) 10 ( H ) 0.003 10 2 0.46 Mg, dis2( mol / cm. s) 0.0854 ( H ) Mg, precip ( mol / cm 2. s) k Mg ( K OH a CO 2 3 K K e CO CO 3 3 K K 6362.76 T ( K ) OH OH K CO 3 a OH ) M (1 M Mg ) 45

Incorporating the Morphological Changes in the Kinetic Model 90 o C (Low) 125 o C (Medium) 150 o C (High) Temperature conditions chosen based on the single step carbonation rate data (Gadikota, PCCP 2014) Assume changing volume of rock due to surface passivation: n <0, increasing surfaces available (e.g., through fractures): n> 0 no changes: n = 0 Rate Rate time V V time time 0 time 0 Simulations set up in PhreeqC (chemistry software) n 46

Role of Carbon Mineralization in Enabling Geologic Carbon Storage Develop thermodynamically downhill routes for permanent CO 2 storage with reduced monitoring needs To develop a comprehensive understanding of CO 2 mineralization behavior and its implications for CO 2 storage potential and costs Comparison of dissolution rates and direct mineralization rates Determination of the feedback mechanisms due to chemo - morphological - mechanical changes Evaluation of the impacts on CO 2 storage potential and net CO 2 emission reductions & costs 48

What is the impact on net CO 2 emissions if olivine is reacted at 25 o C vs. 155 o C? 25 o C 155 o C Kirchofer et al., Energy & Envr. Sci., 2012 Experimental evidence of higher olivine carbonation kinetics at elevated temperatures translates into overall gains in CO 2 emissions reduced. 49

What is the carbon storage potential via ex-situ mineralization approaches? Kirchofer et al., Energy & Envr. Sci., 2012 Natural alkalinity sources a assumes a production rate of 18 Mt per year, equivalent to U.S. lime production, and b of 760 Mt per year, equivalent to U.S. sand and gravel production Carbon mineralization contributes to the portfolio of options available for reliable carbon storage 50

Direct Carbon Mineralization: Compositional Effects Reaction time 0.5 h 5.0 h 1.0 h 6.0 h * this study Storage approach US$/ton CO 2 Geologic carbon storage Geologic carbon storage: monitoring and storage 0.5-8 0.1-0.3 Mineral carbonation 50 100* Estimates from IPCC Special Report on Carbon Capture and Storage, 2005 alumino-silicate bearing minerals or rocks In-situ storage potential silicate bearing minerals Ex-situ storage potential Significant uncertainties exist in reporting costs for carbon mineralization Potential of using waste heat at a power plant as heating source Availability of pre-ground mine tailings as low-cost substrates Potential reuse of industrial acidic and alkaline waste water streams Tailored use of passive vs. active carbonation approaches 51

Conclusions and Summary Development of consistent experimental methodologies has led to an advanced understanding of carbon mineralization rates. Significant variations in predicted mineralization rates translates into field scale uncertainties in monitoring costs. Mineralization rates are accelerated at higher temperatures and in water-rich environments => potential for utilizing industrial waste heat or waste water may result in significant offset of overall energy costs. Advanced mineralization approaches have the potential to be used in industrial decarbonization in addition to enabling clean fossil energy production. 53

Metastability in MgO-CO 2 -H 2 O Systems Magnesite is the most stable and least soluble carbonate under most conditions (including P CO2 ) Despite this, magnesite is seldom the main product reported in literature: - Brucite: Mg(OH) 2 - Lansfordite: MgCO 3 5H 2 O - Nesquehonite: MgCO 3 3H 2 O - Hydromagnesite: Mg 5 (CO 3 ) 4 (OH) 2 4H 2 O - Magnesite: MgCO 3 Driven by reaction kinetics, given enough time, magnesite should form 54

Effect of Temperature on Mg(OH) 2 Slurry Carbonation At 30 ºC Make Nesquehonite At 150 ºC Make Hydromagnesite At 200 ºC Make Magnesite Fricker et al., I&ECR, 2014. 55